I don’t think this was particularly modeled on MS Word. The incremental update feature was introduced with PDF 1.2 in 1996. It allows to quickly save changes without having to rewrite the whole file, for example when annotating a PDF.
Incremental updates are also essential for PDF signatures, since when you add a subsequent signature to a PDF, you couldn’t rewrite the file without breaking previous signatures. Hence signatures are appended as incremental updates.
Incremental updates are also essential for PDF signatures, since when you add a subsequent signature to a PDF, you couldn’t rewrite the file without breaking previous signatures. Hence signatures are appended as incremental updates.